1. Field of the Invention
The present invention concerns a method of and an apparatus for manufacturing an endless ribbon such as an ink ribbon used by a printer and, more particularly, it relates to a method of and apparatus for manufacturing an endless ribbon which is adapted to join the two ends of the ribbon by welding them together and, subsequently, remove the superfluous ends of the ribbon by cutting them.
2. Description of the Prior Art
Various kinds of printers are used as printing devices such as those for word processors or computers, but the most common type is a wire-dot printer which strikes fine wires through an ink ribbon against a sheet of paper at high speed.
Ink ribbons used in wire-dot printers are fabricated by impregnating a synthetic resin fabric with ink, and endless ribbons are generally used since they can be used continuously by circulating without causing problems by needing to be exchanged or rewound.
In a known apparatus for manufacturing such endless ribbons, the two ends of a ribbon are overlapped in a cross shape with identical surfaces facing each other, and ultrasonic waves are applied to a central part of the overlapped portion to weld together the overlapped portion and simultaneously cut off superfluous ribbon ends, as described in, for example, Japanese Patent Publication Sho 54-2235 (1979) (cited in the specification of Japanese Patent Laid-Open Sho 63-132030). In another known apparatus, the two ends of a ribbon are overlapped in parallel one above the other with different surfaces facing each other, and ultrasonic waves are applied to weld together a central part of the overlapped portion. Subsequently, the superfluous ribbon ends are cut off by using scissors or a similar tool designed especially for this purpose.
In the existing apparatus for manufacturing endless ribbons described above, the former apparatus that uses the method of simultaneous welding and cutting the ribbon has a problem in that the tensile strength of the ribbon in the welded portion is low. The latter apparatus that cuts off the superfluous ribbon ends also involves a problem in that it requires a manual operation for cutting off the superfluous ribbon ends, which is time-consuming and the quality of the finished products varies.
In view of the above situation, the present inventor has previously proposed an apparatus for manufacturing an endless ribbon which is adapted to cut off superfluous ribbon ends by using a laser beam after welding the ribbon ends together.
Japanese Patent Laid-Open Sho 63-132030 proposes on for manufacturing endless ribbon has various advantages, such as the superfluous ribbon which ends can be cut as short as possible with minimal loss, shaping is easy, and the width of the final weld line can be minimized. However, heating is applied a total of three times to positions near the welded portion, that is, during the welding, during the cutting off of the superfluous ribbon ends and during final shaping, and this heating causes a problem in that the impregnated resin component in the welded portion is melted and then solidified, in other words, the portion becomes stiffened which deteriorates the flexibility and softness of the fibrous ribbon.